The present invention is directed, in general, toward test apparatus and, more particularly, toward apparatus for determining the presence of a analyte in a sample.
Recently, various methods have been developed for detecting a variety of analytes in a sample where the analyte is capable of reacting with a reagent to produce a particular color or hue. The color which is produced can, in turn, be detected as, for example, by using a spectrophotometric instrument.
Prior methods relied upon the detection of a analyte in a liquid cuvette, such as the well of a translucent microtiter plate. Typically, the microtiter plate included a plurality of wells each containing the liquid reactants with a minimum depth of about 70 mm through which the light must pass in order to determine the presence of analyte. Instruments used with these prior microtiter plates typically transmitted a calibrated light beam from one side of the plate through each well of the plate and detected, on the other side of the plate, the amount of light transmitted through the liquid material and the translucent plate to determine the presence of analytes contained in the liquid material.
There are currently numerous manufacturers of these plates and the associated instruments, to read the reaction occurring in the wells thereof. Plates are sold having both unmodified and modified surfaces. Some microtiter plates are pre-sensitized for use as preformulated diagnostic tools for a broad array of analytes.
When first introduced, the microtiter plate and reader systems were useful in their original design and became an industry workhorse. However, with the development of more sophisticated techniques and improved sensitivity current designs have failed to keep pace.
Some of the techniques which have become increasingly useful in detecting a analyte in a sample use antibodies. In these techniques the antibody is used to detect the presence of the analyte, in this case an antigen, for which the antibody is specific. Over the last several years, the sensitivity of antibody-based tests have increased such that less liquid volume within the wells of the microtiter plate is required. However, a need exists for a highly sensitive and inexpensive instrument to measure a reaction in a substantially liquid-free format.